Method and apparatus for making thermochromic battery tester

ABSTRACT

A battery tester device that may be integrated into a label of battery. The battery tester device includes first dielectric layer, a conductive layer adjacent the first dielectric layer, a temperature sensitive indicator layer in thermal contact with the conductive layer, and thermal insulation adjacent the conductive layer. The thermal insulation includes a second dielectric layer and thermally insulative material combined with the second dielectric layer for enhancing the structural strength of the second dielectric layer.

RELATED APPLICATION

This application is a divisional of application Ser. No. 08/721,633filed on Sep. 26, 1996, now U.S. Pat. No. 5,925,480.

FIELD OF THE INVENTION

The present invention relates in general to devices for testing thecapacity of a battery and, more particularly, to a battery tester thatmay be integrated into the label of a battery.

BACKGROUND OF THE INVENTION

Batteries of all types, whether frequently or rarely used, dischargewith the passage of time. Accordingly, when placed into service, thebattery or batteries that provide the energy source for electronicequipment such as flashlights, toys, radios, audiocassette players,compact disc players and myriad other devices, may or may not havesufficient charge to power the equipment. As a consequence, a variety ofdevices have been proposed whereby a user can determine a battery'senergy level with reasonable certainty.

Perhaps the earliest known battery testers, which remain in commonusage, include specifically designated voltmeters and ammeters. Althoughquite accurate when properly calibrated and operated, such devices arecumbersome to use, must be carefully maintained and stored, and can berather expensive.

More recently, battery testers have been incorporated into batterypackaging containers. These testers, generally referred to asthermochromic testers, normally compromise an electrically conductivelayer in thermal contact with a temperature sensitive color indicatorlayer. When the ends of the conductive layer are contacted with abattery's terminals, electronic current flows through and creates heatin the conductive layer. The heat so generated causes a change in theindicator layer if the voltage of the battery exceeds a predeterminedthreshold. Tester devices of this sort are somewhat difficult to operatebecause a user must precisely align and maintain contact of the tester'sterminals with the battery's terminals to achieve reliable results. Inaddition, the tester is usually capable of testing the condition of onlya single size of battery, e.g., a AA battery. Moreover, the batterypackaging itself, which is bulky and susceptible to damage, must beretained and carefully stored, although it is commonly misplaced ordiscarded as trash.

Even more recently, thermochromic testers have been incorporated intothe labels encasing the batteries themselves. Examples of such built-intesters may be found in U.S. Pat. No. 5,015,544. Testers of this sortare in immediate contact with the typically metal housings of thebatteries to which they are attached. As such, the battery may act as aheat sink for the heat generated during operation of the tester. If notcontrolled this loss of heat may hinder the function of both the testerand the battery. For instance, to achieve the threshold temperaturesufficient to effect a change in the color indicator layer, the testermay have to be operated for a longer period of time than would otherwisebe desired, thereby prematurely draining the battery of useful energy.Additionally, the loss of tester heat into the battery may cause thetester to produce inaccurate readings of the battery's strength, i.e.,the tester might indicate the battery to be drained when in fact thebattery is still useful. In these circumstances, a user might mistakenlydiscard good batteries in reliance upon the errant readings of thetester.

To alleviate battery heat sink problems, U.S. Pat. Nos. 5,059,895,5,223,003, 5,389,458, 5,393,618, 5,409,788 and 5,538,806 have proposedplacement of thermal insulation means between the conductive layer of athermochromic battery tester label and the battery housing. The thermalinsulation means may comprise, inter alia, a layer of release paper,plastic strips, foamed plastic, foamed ink, embossed or printed inks,adhesives, cloth and the like. These insulation materials may bedeployed as substantially continuous layers or as discontinuousarrangements defining one or more air pockets between the conductivelayer and the battery housing. Indeed, because of the extremely lowthermal conductivity of air, when the insulating material isdiscontinuous in layout, the insulating characteristics of the compositethermal insulation means, i.e., insulation material and air gaps, aresuperior to a continuous layer of insulating material having no airgaps. U.S. Pat. No. 5,223,003 in particular discloses thermochromicbattery tester thermal insulation means including solid spacers formedof foamed plastic and shaped to define an air pocket. It will beappreciated that such a construction combines the thermal insulationbenefits of the air pocket, the plastic material and air contained inthe plastic material.

When cured, foamed plastics or inks comprise a matrix of plastic or inkmaterial which entraps bubbles of a gaseous matter, most commonly air.It is axiomatic that there is a direct relationship between the volumeof entrapped gas and the thermal insulation characteristics of theinsulation material: the greater the volume of entrapped gas, the morethermally insulative the material, and vice versa. However, there is aninverse relationship between entrapped gas volume and the structuralstrength of the insulating material. That is, as the "hollow" or "void"space of a foamed plastic increases, the material's ability to resistexternally applied compressive force decreases, and vice versa. Hence,the volume of entrapped gas cannot exceed a threshold level which wouldcompromise the insulating structure's capacity to withstand externallyimposed forces associated with ordinary manufacturing shipping, handlingand usage of a typical battery. Yet, this threshold entrapped gas levelmay not be sufficient to impart a meaningful contribution to the thermalinsulation characteristics of the material.

A need exists, therefore, for a thin thermal insulation means for athermochromic battery tester that combines optimum thermal insulationproperties with high structural strength and that will functioneffectively with any battery of conventional dimensions.

SUMMARY OF THE INVENTION

The present invention contemplates novel thermal insulation means, athermochromic battery tester device incorporating such thermalinsulation means, a battery label including such a tester device, abattery including such a battery label, and methods of constructing thethermal insulation means, thermochromic battery tester device, batterylabel and battery.

The thermal insulation means of the present invention preferablycomprises at least one layer of flexible, thermally insulative,dielectric matrix material within which is embedded structurally strongthermally insulative material. A presently preferred material for thesepurposes is a plurality of miniature spheres usable alone or incombination with other insulative materials such as fibrous and/orparticulate materials. The spheres are preferably hollow and encapsulatea thermally insulative substance, desirably a gaseous substance such asair. The spheres themselves may be fabricated from any thermallynonconductive substantially rigid material such as glass or plastic thatcan be formed into extremely small spheres by processes known in theart.

Moreover, by virtue of their spherical shape, which shape inherentlypossesses exceptional force distribution and force transmissioncharacteristics, the spheres provide an excellent means for resistingthe impacts and other mechanical shock normally encountered by abattery.

For best results the sphere-containing thermal insulation means of thepresent invention is preferably manifested as a random or patterneddiscontinuous arrangement. Thus, when the thermal insulation means isdisposed between a battery housing and a conductive layer of athermochromic battery tester, one or more air pockets are formed betweenthe conductive layer and the battery housing. In this way, astructurally strong and impact resistant thermal insulation means isrealized which makes optimum use of the excellent thermal insulationproperties of air, including both the air in the air pockets and thatencapsulated in the spheres in combination with the thermally insulativematerial from which the spheres are formed and the matrix materialwithin with the spheres are embedded.

The superior thermal insulation characteristics of thermal insulationmeans according to the present invention thereby functions to enhanceperformance of a thermochromic battery tester with which the tester maybe deployed and to reduce drain on a battery that may be evaluated bysuch a tester.

More particularly, the present thermal insulation means uses the lowthermal conductivity of air to considerable advantage.

As a consequence, the tendency of the battery to function as a heat sinkfor the thermal energy generated by the battery tester's conductivelayer is effectively vitiated by the instant thermal insulation means.This virtual thermal isolation of the tester's conductive layer from thebattery housing enables the tester to rapidly provide a reliable readingof a battery's strength. That is, essentially all of the thermal energycreated when battery current passes through the conductive layer of thebattery tester is beneficially directed toward the thermochromicmaterial of the battery tester and not uselessly dissipated by thebattery. This phenomenon, in turn, causes the heat sensitivethermochromic material to rapidly achieve a threshold temperaturesufficient to produce a visible change in the thermochromic material.Consequently, a user can obtain in about one second or less a reliablereading of a battery's capacity. By contrast, comparably constructedthermochromic battery testers heretofore known in the art may takeseveral seconds to achieve a meaningful reading, especially when thebattery's power level is low.

In addition, because the heat generated by the conductive layer of thebattery tester is put to more efficient use when associated with thethermal insulation means of the present invention, and also because lesstime is required to perform a test, less current is drawn from thebattery during a test procedure. Therefore, use of a thermochromicbattery tester label incorporating the thermal insulation means of thepresent invention reduces drainage of a battery's energy supply andprolongs the useful service life of the battery.

Moreover, by virtue of its low thermal conductivity, the instant thermalinsulation means may be used with conductive layers having greaterresistance than those presently employed in thermochromic battery testerlabels. Alternatively, the thermal insulation means of the presentinvention may permit a reduction in the volume of material required forconductive layers formed from conventional materials. In either case,the time required to perform a reliable battery test may be even furtherreduced. And, the materials and fabrication costs of a tester deviceincorporating the present thermal insulation means may becorrespondingly reduced.

Other details, objects and advantages of the present invention willbecome apparent-as the following description of the presently preferredembodiments and presently preferred methods of practicing the inventionproceeds.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will become more readily apparent from the followingdescription of preferred embodiments thereof shown, by way of exampleonly, in the accompanying drawings, wherein:

FIG. 1A is a top plan view of a first preferred embodiment of a batterytester device according to the present invention;

FIG. 1B is a perspective view of the battery tester device of FIG. 1Aincorporated into a label affixed to a battery;

FIG. 2A is a top plan view of a further preferred embodiment of abattery tester device according to the present invention;

FIG. 2B is a perspective view of the battery tester device of FIG. 2Aincorporated into a label affixed to a battery;

FIGS. 3A and 3B are enlarged cross-sectional views of a switch portionof the battery tester according to FIGS. 1A and 1B affixed to a batteryand depicting the switch of the tester device in deactivated andactivated condition, respectively;

FIG. 3C is an exploded view of the essential layers of a thermochromicbattery tester device arranged in accordance with the present invention;

FIG. 4 is a top plan view of thermal insulation means constructedaccording to the present invention;

FIG. 5 is an enlarged cross-sectional view of the thermal insulationmeans of FIG. 4 disposed in a battery label affixed to a battery, thecombination of which also forms a part of the present invention;

FIG. 5A is an even further enlarged cross-sectional view of the thermalinsulation of the present invention encircled within arrow 5A of FIG. 5;and

FIG. 6 is a schematic view of an apparatus and method for assembling athermochromic battery tester device according to the present invention.

DETAILED DESCRIPTION OF THE INVENTION

Referring to the drawings wherein like reference characters designatelike or corresponding parts throughout the several views, there is shownin FIG. 1A a battery tester device according to a first presentlypreferred embodiment of the invention, which device is identifiedgenerally by reference numeral 10. Tester device 10 comprises indicatingmeans preferably constructed as an at least partially transparentindicating chamber 12 in responsive contact with a portion of anelectrically conductive material layer 14. The indicator chamber 12contains at least one layer of thermally sensitive indicating material16 which undergoes a visible change when subjected to a predeterminedthreshold temperature.

FIG. 1B depicts a battery 18 encased by a label 20 which incorporatesthe battery tester device 10. Battery 18 has an anode or first terminal22 at one end thereof and a cathode or second terminal at an oppositeend (not shown). As is known in the art, the external housing of thebattery 18 extending between the first and second ends of the batterymay be fabricated from metal. In many such instances the metal housingmay be in electrical communication with one of the anode or cathode.Accordingly, the metal housing is electrically insulated from the otherof the cathode and anode. Under those circumstances, the metal batteryhousing effectively serves as an extension of either the anode orcathode to which it is electrically connected.

The opposite ends of the conductive layer 14 define first and secondterminals 24, 26 which are adapted for respective contact with the firstand second terminals of battery 18. The conductive layer 14 may suitablycomprise any conductive material such as metal or metal alloy preferablyformed as a thin film. Conductive layer 14 may be preformed and thenattached to a substrate such as a dielectric material including, withoutlimitation, paper, plastic or cloth. Alternatively, as will be describedin greater detail in connection with the discussion of FIG. 5,conductive layer 14 may comprise a layer of metallized coating or inkwhich is applied on a suitable substrate. Moreover, the conductive layer14 may assume any desired shape. For optimum performance, however, theconfiguration of the conductive layer 14 should be such that itsresistance in the region corresponding to the indicator chamber 12 is atleast as great as in the remainder of the conductive layer. The heatgenerated by the conductive layer 14 is dependent on its own inherentresistance, as well as the voltage and current output and thus thestrength of a battery, e.g., battery 18, that is to be tested by testerdevice 10.

The indicating material 16 can be any thermochromic material such asliquid crystal compositions and thermochromic inks, among others, thatwill undergo a visible change when the voltage of the battery 18 dropsbelow or, more typically, exceeds a predetermined voltage. Theindicating material 16 may be such that its visible change occurs as aone-time irreversible event. More preferably, however, the visiblechange is reversible in order that the battery may be repeatedly testedat the discretion of the user.

The visible change may be a color change such as from a color tocolorless, colorless to a color, or one color to another color.

Suitable indicating materials may include thermally sensitive liquidcrystal compositions such as those of cholesteric type includingcholesteryl oleate, cholesteryl chloride, cholesteryl caprylate and thelike. Examples of suitable thermochromic inks include those comprised ofa dye, developer and desensitizing agent that are disclosed in U.S. Pat.No. 4,835,475, herein incorporated by reference.

The indicating materials such as thermochromic inks can be used singlyor combination. For example, different layers of indicating materialscould be employed whereby the different layers are activated atdifferent temperatures and can be designed to change different colors atdifferent temperatures. Such an arrangement may be useful inestablishing a quantitive gradient type indicator means at a particularambient temperature or a qualitative indicator means that may providereliable readings at varying ambient temperatures.

The tester device 10 may also be fabricated so that it indicates aquantitive measure of a battery's capacity such as a load or no-loadvoltage threshold. For example, one can select a no-load voltagethreshold which is indicative that the battery is about 25% exhausted,about 50% exhausted, etc., as may be suitable for intended purposes.Alternatively, the cross sectional area of the conductive layer 14 maybe varied in the region thereof corresponding to the indicator chamber12. In this way, a gradient of heat may generated along the conductivelayer 14 during testing.

This heat in turn is transferred to the indicating chamber 12 and theindicating material 16 contained therein. Under these circumstances, thetester device 10 or the battery label 20 within which it may beincorporated is preferably provided with a calibrated indicating scaleto display the remaining capacity of the battery being tested. Stillfurther, the indicating chamber 12 and indicator material 16 may bedesigned to convey a simple qualitative measure of the battery'scondition such as a "GOOD" or "REPLACE" message.

In addition, the dimensions and resulting resistance of the conductivelayer 14 can be adjusted for any battery size, voltage or currentrequirements. And, from Ohm's law the battery tester device 10 can becalibrated for volts, current, remaining service life, state of charge,or any combination thereof.

When mounted to a battery such as battery 18 the tester device 10 may bein continuous contact with the first and second terminals of thebattery. As such, the device 10 will continuously operate and theindicator chamber 12 will undergo a visible change only when the outputvoltage of the battery falls below a predetermined value. Thedisadvantage of continuous operation, however, is that such a testerdevice imposes a constant drain on the battery's energy supply.

It is more preferable that the tester device 10 include at least oneswitch 28 (as in FIGS. 1A and 1B) or two switches 28 (as in FIGS. 2A and2B). The benefit of at least one switch 28 is that the tester device 10is normally biassed to be in an "OFF" state. Hence, the tester device isonly activated when the switch 28 is on, thus preventing a constantdrain on the battery. The construction and operation of switch 28 isbest appreciated by reference to FIGS. 3A and 3B.

As seen in FIGS. 3A and 3B, a portion, in particular the switch portion,of a battery label 20 incorporating a tester device 10 according to thepresent invention is shown affixed to a battery 18. FIG. 3C provides anexploded view of the essential components of the tester device 10 in anarrangement consistent with the present invention. Referringcollectively to FIGS. 3A, 3B and 3C, the battery label 20 preferablycomprises a flexible substrate layer 30 of dielectric material such aspaper, cloth or, more preferably, a polymeric material such aspolyethylene, polyester, polypropylene or polyvinylchloride which may bemetallized or non-metallized. The dielectric material is chosen so as toprovide a measure of electrical and thermal insulation between thebattery 18 and the working elements of the battery tester. Disposedbetween the battery 18 and the flexible substrate layer 30 is a layer ofadhesive 32 which may be any conventional pressure sensitive or curableadhesive. Desirably, adhesive layer 32 is a pressure sensitive adhesivecarried by the substrate layer 30 for facilitating high speed placementof the label 20 onto the circumference of the battery 18 usingconventional label attachment apparatus and methods.

Disposed on the surface of the substrate layer 30 opposite adhesivelayer 32 is the conductive layer 14. To minimize the cross-sectionalprofile of the battery label 20 the conductive layer 14, as previouslymentioned, preferably comprises a thin layer of conductive material suchas metallized coating or ink which may be deposited on substrate layer30 using conventional coating or printing techniques. This conductivematerial may be, for example, silver, nickel, iron, copper, lead and thelike, or mixtures thereof, and is preferably dispersed in a bindermaterial to form a conductive ink. Silver is the preferred material andpreferred thicknesses of the conductive layer are contemplated to beabout 0.0001 to about 0.002 inch (about 0.00254 to about 0.0508 mm).

According to a presently preferred construction, the thermochromicindicating material 16 is deposited at a desired location on the surfaceof the conductive layer 14 opposite the substrate layer 30. With theindicating material so placed, the label 20 also should comprise anouter protective layer 36 preferably formed from a film material similarto substrate layer 30. The protective layer 36 would thus enclose thelabel assembly and define the sealed indicating chamber 12 forindicating material 16 shown in FIGS. 1A, 1B, 2A, 2B and 5. To assureperception of visible changes in the indicator material 16 during abattery test, the protective layer should be at least partiallytransparent in the region thereof corresponding to the indicatingchamber 12.

The indicating chamber 12 may also be formed in other acceptable ways.For example, an intermediate layer may be provided as two sublayerswhereby the indicator material 16 may be deposited at a desired locationon one of the sublayers. Thereafter, the sublayers may be laminatedtogether and then applied to the conductive layer 14, thereby renderingthe protective layer 36 optional.

It will be understood that the layers described above represent apresently preferred embodiment of label 20 and can be altered,rearranged or assembled in many ways to provide the label 20 with abattery tester circuit. Moreover, the labels useful in the presentinvention may comprise additional insulation layers, graphics layers,protective layers, and the like. Suitable materials for use as thedifferent layers are those typically used in battery labels and includeplasticized or unplasticized polyvinyl chloride, metallic films, paperand the like, and they may be prepared and applied by known methods suchas coating, printing and laminating the layers together. Further, thelabel 20 and any variants thereof within the scope of the presentinvention can be made in the form of individual sheets having a seam oras a shrinkable tube in which a battery may be encased. To prepare thelabel 20 as a shrinkable tube, after forming the label as generallydescribed above, the label is placed around a mandrel and weldedlengthwise to form a tube. The tube is then flattened, and wound on aroll whereupon it is ready for use.

Additionally, the above described thermal insulation means, testerdevice and battery label of the present invention may be used with a drycell battery (as described) or a wet cell battery, and with bothrechargeable and non-rechargeable batteries.

Comparison of FIGS. 3A and 3B reveals that the tester label 20 isactivated by depressing the label in the area of switch 28. To assureproper functioning of the switch 28, the substrate layer 30 ispreferably provided with an opening 38. Because of the presence ofopening 38 in substrate layer 30, a similar opening 39 is created inadhesive layer 32 in alignment with opening 38, which openings are alsoshown in FIG. 3C. Accordingly, the portion of the conductive layer 14associated with the switch 28 may pass through openings 38 and 39 upondepression of the switch and contact the battery housing, therebyclosing the tester circuit to initiate a testing procedure. Removingpressure from the switch 28 allows the conductive layer 14 in the regionof the switch 28 to retract to the position shown in FIG. 3A, therebyopening the switch and ceasing the test procedure.

In the tester device shown in FIGS. 2A and 2B, wherein two switches 28are provided, both switches must be simultaneously depressed to carryout a testing procedure.

FIGS. 4, 5 and 5A illustrate on an enlarged scale, the particulars of apresently preferred embodiment of thermal insulation means constructedin accordance with the present invention, which means are generallyidentified by reference numeral 40. It will be appreciated that thedimensional aspects of the thermal insulation means 40 and the otherlayers of the label 20 are greatly exaggerated to clearly represent thestructural features of the invention. In an actual construction, thecomposite structure of label 20 in the region of the indicating chamberwould be virtually flat. As such, the presence of the tester deviceconstitutes a negligible contribution to the cross-sectional profile ofthe battery label and, from a tactility perspective, is essentiallyindistinguishable from the remainder of the battery label. As shown inFIGS. 3C and 5, thermal insulation means 40 is disposed so as to be ingeneral alignment with the indicating chamber 12. Thermal insulationmeans 40 may be located on the surface of the substrate layer 30opposite conductive layer 14. Preferably, however, the thermalinsulation means 40 is situated, as illustrated, between the conductivelayer 14 and the substrate layer 30. The thermal insulation means may bepreformed as a separate component and then applied to either thesubstrate layer 30 or the conductive layer 14. According to a presentlypreferred method, thermal insulation means 40 is applied by coating orprinting substrate layer 30 with a discrete quantity of curable ink orsimilar coating material using standard lithographic, flexographic,gravure or screen printing processes.

The thermal insulation means 40 preferably comprises at least one layerof thermally insulative dielectric matrix material 41 such as adielectric ink or a similar coating composition which is applied tosubstrate layer 30. The preferred thickness of the matrix material 41 isfrom about 2 to about 5 mil in order to minimize the cross-sectionalprofile of a label within which tester device 10 may be incorporated.Most preferably, thermal insulation means 40 is applied to substratelayer 30 in a discontinuous arrangement 42. The areal dimensions of thediscontinuous arrangement 42, as indicated by length "L" and width "W"in FIG. 4, should be at least as great as those of the indicatingchamber 12 (FIGS. 1A, 1B, 2A and 2B). Most preferably, the area of thediscontinuous arrangement 42 is somewhat greater than that covered bythe indicating chamber 12. By exceeding the perimetrical boundary of theindicating chamber 12, the discontinuous arrangement 42 assures thatheat generated by the conductive layer 14 in the region of theindicating chamber 12 is effectively isolated from an underlying batteryand advantageously directed toward the indicating chamber.

The discontinuous arrangement 42 may be a random or amorphous shape.Preferably, however, the discontinuous arrangement defines anidentifiable pattern, an illustrative but non-limitative example ofwhich is depicted in FIG. 4. In that figure, the pattern established bythe discontinuous arrangement 42 is a generally open latticeconfiguration defining a plurality of air pockets 44. Air pockets 44 maybe any polygonal or curvilinear shape and can be of uniform ornon-uniform sizes. The pattern for defining the air pockets 44 does notnecessarily have to produce one or more air pockets of closed-cellconfiguration. That is, the discontinuous arrangement 42 may be simply aplurality of substantially parallel rows of material, which rows may bestraight, curved, sinusoidal, saw-toothed or otherwise defining anidentifiable pattern, whereby one or both ends of individual air pocketsbounded by the rows of material may be open at the perimeter of thediscontinuous arrangement.

The term "discontinuous" when used to describe the discontinuousarrangement 42, therefore, merely means that the thermal insulationmeans 40 of the present invention defines a practical measure of openspace within its areal boundaries. This open space, i.e., one or moreair pockets 44, must provide a meaningful "air gap" contribution to thethermally insulative characteristics of the thermal insulation means 40.A significant degree, although not necessarily a preponderance, of openspace thus distinguishes the discontinuous arrangement 42 of thermalinsulation means 40 from typical "continuous", i.e., substantiallyimperforate, thermal insulation means such as, for example, an unbrokenlayer of dielectric ink, an unbroken sheet of paper or plastic film,tightly woven cloth or densely constructed non-woven cloth.

As perhaps most clearly seen in FIG. 5A, which is a further enlargedcross-sectional view of the thermal insulation of FIG. 5 encircled byarrow 5A, thermal insulation means 40 further comprises means 46embedded in the matrix material 41 of the discontinuous arrangement 42for enhancing the structural strength of the thermal insulation means.Means 46 may comprise any suitable thermally insulative material, forexample, fibrous or particulate material or, more preferably, aplurality of miniature spheres usable alone or in combination with otherstrength-enhancing insulative materials, e.g., the aforementionedfibrous and/or particulate materials. The spheres 46 are preferablyhollow and encapsulate a thermally insulative substance, desirably agaseous substance such as an inert gas (e.g., argon, neon, helium, andthe like) or air which, most preferably, has been dehumidified prior toencapsulation. The spheres 46 may be fabricated from any substantiallyrigid material such as glass or plastic (e.g., styrene acrylic polymersand the like) that can be formed into extremely small spheres of frombetween 0.4 μm to about 50 μm in diameter by processes known in the art.Suitable spheres for purposes of the present invention include glassspheres manufactured by Potters Industries Inc. of Parsippany, N.J.having mean particle sizes of less than about 50 μm, more preferablyless than 20 μm, and most preferably less than about 10 μm.

As mentioned previously, the thermal insulation means 40 may bepreformed into a predetermined discontinuous arrangement 42 andthereafter applied to substrate layer 30 (FIG. 5). Alternatively, andmore preferably, the thermal insulation means 40 may be applied as acurable dielectric ink or similar coating to the appropriate surface ofsubstrate layer 30 and in the desired discontinuous arrangement 42 usingconventional printing or coating processes. In either case, the spheres46 may be added to the matrix material of the thermal insulation meansafter deposition of such material. More preferably, however, the spheres46 are combined and mixed with the matrix material prior to depositionto ensure substantially uniform distribution of the spheres throughoutthe matrix material upon deposition thereof.

Because of their substantially spherical shape, which shape inherentlypossesses exceptional force distribution and force transmissioncharacteristics, the spheres 46 provide an excellent means for resistingthe impacts and other mechanical shock encountered by a battery undernormal manufacturing, shipping, handling and usage.

The thickness "T" (FIG. 5A) of the thermal insulation means 40,including spheres 46 embedded therein, need not exceed more than about 5mil. Such thickness has been discovered to be sufficient to reconcilethe heretofore conflicting objectives of high structural strength,exceptional thermal insulation capacity and low cross-sectional profile.

The thermal insulation means 40 of the present invention beneficiallycombines the thermal insulation properties of the air pocket(s) 44, thematerial of which the spheres 46 are formed, the air encapsulated in thespheres, and the matrix material (e.g., dielectric ink) which binds thespheres into a cohesive mass.

The virtually complete thermal insulation provided by thermal insulationmeans 40 thus effectively eliminates the tendency of a battery tofunction as a heat sink for the thermal energy generated by theconductive layer 14 of the battery tester device 10 when the testerdevice is incorporated into a battery label such as label 20. Thisvirtual thermal insulation of the tester device conductive layer 14 fromthe battery housing enables the tester device to rapidly provide areliable reading of a battery's capacity. That is, nearly all of thethermal energy created when battery current passes through theconductive layer 14 in the region of the indicating chamber 12 isdirected toward the thermochromic material 16 contained within theindicating chamber and not uselessly dissipated by the battery. Thisphenomenon, in turn, causes the heat sensitive thermochromic material 16to achieve a threshold temperature sufficient to produce a rapid visiblechange in the thermochromic material. Consequently, a user can obtain inabout one second or less a reliable reading of a battery's capacity. Bycontrast, comparably constructed thermochromic battery testersheretofore known in the art may take several seconds to achieve ameaningful reading, especially when the battery's power level is low.

In addition, because the heat generated by the conductive layer 14 ofthe battery tester 10 is put to more efficient use when associated withthe thermal insulation means 40 of the present invention, and alsobecause less time is required to perform a test, less current is drawnfrom the battery during a test procedure. As a consequence, use of athermochromic battery tester label 20 incorporating thermal insulationmeans 40 reduces drainage of a battery's energy supply and therebyprolongs the useful service life of the battery.

Moreover, by virtue of its low thermal conductivity, the instant thermalinsulation means 40 may be used with electrically conductive layershaving greater resistance than those presently employed in thermochromicbattery tester labels. Alternatively, the thermal insulation means ofthe present invention may permit a reduction in the volume of materialrequired for conductive layers formed of conventional materials. Ineither case, the time required to perform a reliable battery test may beeven further reduced. And, the materials and fabrication costs of atester device incorporating the present thermal insulation means 40 maybe correspondingly reduced.

The instant thermal insulation means additionally blends theseadvantageous thermal insulation characteristics with the considerableinherent structural strength of the spheres 46 into a rugged structurecapable of withstanding the externally applied forces and similarmechanical rigors unique to battery-mounted thermochromic tester labels.

Referring to FIG. 6 there is shown an exemplary and presently preferred,although not limitative, system for high speed manufacturing ofthermochromic battery tester devices 10 according to the presentinvention.

Construction of the tester devices may be carried out in a "single pass"by printing all graphic and functional layers of a tester device on asingle, flexible base substrate such as substrate 30 which may or maynot be enclosed by a protective outer layer 36, as reflected in FIG. 3C.Alternatively, as depicted in FIG. 6, a tester device may be constructedby printing only selected graphic and/or functional layers on selectedones of two or more flexible substrates and then joining the individualsubstrates together, in a manner to be described hereinafter, to formthe completed tester device 10. The combination of functional elementsof the tester device, graphics and other matter applied to eachindividual substrate may be collectively referred to as a "pass". Wherethere are two or more passes made during the construction of a testerdevice, as there is in the presently preferred system depicted in FIG.6, each pass is identified herein by number, as for example, "firstpass", "second pass", etc. In multiple pass constructions, once eachpass has been printed, the several passes are brought into preciseregistration with one another and joined to form the completed testerdevice.

The first pass of the battery tester manufacturing and assemblingprocess revealed in FIG. 6 is schematically depicted as area 48. The"first pass" is that processing pass in which substrate 36 undergoestreatment. The processing means by which first pass 48 is constructedgenerally comprises a laminate substrate positioner 50, an optionalcorona treatment station 52, at least one thermochromic ink printstation 54, optional decorative ink print station(s) 56, and at leastone conductive ink print station 58.

The second pass of the embodiment disclosed in FIG. 6 is schematicallydepicted as area 60. The "second pass" is that processing pass in whichbase substrate 30 undergoes treatment. The processing means by whichsecond pass 60 is constructed generally comprises base substratepositioner 62, an optional corona treatment station 64, optionaldecorative ink print station(s) 66, a notcher 68, as least one thermalinsulation print station 70, and adhesive print station 72.

Prior to printing on substrates 30 and 36, it is generally preferable tocorona treat the substrates to raise their surface tension or "dyne"levels, thereby enhancing the adhesion of printing inks to thesubstrates. As is known, corona treatment imparts a high voltage, lowcurrent, electrical charge to the surfaces of the substrate. Similarresults may likewise be achieved using plasma treatments and/or otherelectrical, mechanical and chemical surface tension enhancementtreatments known in the art.

If the dyne level of the substrates 30 and 36 is too low, printing inkswill tend to adhere in a non-uniform manner and possibly form ink beadsof non-uniform thickness on the surfaces of the substrates. However, ifthe substrate dyne level is sufficiently raised, the inks will tend toadhere more uniformly and with consistent thickness over the surface ofthe substrates.

Returning to the presently preferred processing steps of the two passembodiment of the present invention depicted in FIG. 6, first pass 48 isconstructed by first positioning, via laminate substrate positioner 50,substrate 36 in corona treatment station 52 where the dyne level ofsubstrate 36 is increased. Substrate 36 is then positioned in at leastone thermochromic ink print station 54 where thermochromic indicatingmaterial 16 of desired configuration and thickness is deposited on thesubstrate. Thereafter, the substrate is positioned into one or moreoptional decorative ink print station(s) 56 wherein decorative inks maybe applied. The inks may be of the same or different colors. Lastly,substrate 36 is positioned in at least one conductive ink print station58 where conductive layer 14 is applied.

Second pass 60, which may be processed simultaneously with or at adifferent time than first pass 48, is constructed by positioning basesubstrate 30 in corona treatment station 64 via base substratepositioner 62. From there, the base substrate 30 may be introduced intoone or more optional decorative ink stations 66 for applying at leastone layer of decorative ink of one or more colors. The base substrate 30may then be introduced into a notcher or similar perforation station 68for creating the aforementioned switch opening(s) 38 (FIGS. 3A and 3B).

Following notching, the base substrate 30 may be coated at at least onethermal insulation print station 70 with thermal insulation material toproduce thermal insulation means 40. As a final treatment operation, thesecond pass 60 concludes with a layer of adhesive being applied byadhesive print station 72 to the surface of substrate 30 intended to belaminated to first pass 48.

First and second passes 48 and 60 may be assembled in simultaneous orseparate operations. When printed simultaneously, the first and secondpasses are preferably printed on substantially parallel rotogravure orsimilar presses. The printed first pass 48 is then brought into preciseregistration with and laminated to second pass 60 at a registeredlaminator 74 as described below. The composite structure then preferablyproceeds through an optional die cutter 76 to separate individualprinted tester devices and a rewinder 78. Prior to rewinding, thecomposite structure is preferably provided with a layer of pressuresensitive adhesive (e.g., element 32 of FIG. 3C) and a release meanssuch as release paper (not shown) to enable rewinding and storage of thetesters devices, as well as to facilitate subsequent attachment of thetester devices to individual battery housings.

When printed in separate operations, the first pass 48 is fully printedand then placed into roll or other form suitable for further processingat a later time. The roll comprising the first pass is then mounted toan unillustrated infeed unit at the registered laminator 74. As secondpass 60 is printed and delivered to the registered laminator 74, thefirst pass is simultaneously unwound, placed into precise registrationwith the second pass and laminated to the second pass at the registeredlaminator 74. The composite structure so produced may then proceed todie cutting and rewinding stations 76 and 78.

In two or more pass constructions, it is essential to the successfulassembly and operation of a tester device that the individual passes arealigned and joined together such that the various functional componentsof the device are in proper electrical communication with one anotherand that the graphic layers are aligned to produce the desired visualeffect. To do so, the various passes are preferably aligned and joinedtogether through an automated and continuously self-adjustingregistration and lamination process at registered laminator 74.

Registered lamination in accordance with the present invention may beachieved via suitably configured and cooperating automatic web tensioncontrol means (not illustrated) employed in conjunction with cooperatingautomatic web registration means (also not illustrated) working inconcert at registered laminator 74 to produce two or more pass testerdevices. An exemplary arrangement may include a model number S-3000 webregistration control device and a model number S-2152 web tensioncontrol device, both manufactured by The Bobst Group, Inc. of Roseland,N.J. Such a system may be used to control the first pass 48 as it isunwound from the infeed unit at the registered laminator and joined withthe second pass 60 as the second pass exits the press. Alternatively,registered laminating may be carried out in an offline process whereboth passes 48, 60 have been previously printed and rewound.

Critical to the automated registered lamination process is tocontinuously monitor the stress characteristics of each pass 48, 60during production. Improper stress placed on first pass 48, forinstance, which pass is typically stretched relative to pass 60 duringlamination, may cause delamination or curling of the passes once joined.

To achieve precise, substantially real-time control, the registeredlaminator preferably further comprises web position sensing means (notshown) for monitoring certain physical characteristics of the firstand/or second passes 48 and 60 as they traverse the registeredlaminator. Such web sensing means are preferably electronicallyconnected to a suitable system control device, e.g., a microprocessor(not shown), which continuously monitors the web sensing means andsimultaneously controls the functions of the web tension control meansand the web registration control means responsive to web position datareceived from the web sensing means. The web tension control means andweb registration control means are preferably adaptable to control therelative tensions and registrations of either or both of the first andsecond passes 48, 60.

Although the invention has been described in detail for the purpose ofillustration, it is to be understood that such detail is solely for thatpurpose and that variations can be made therein by those skilled in theart without departing from the spirit and scope of the invention exceptas it may be limited by the claims.

What is claimed is:
 1. A method of manufacturing an electronic device,said method comprising the steps of:(a) printing a surface of a firstsubstrate with a first printable ink to produce a first conductivecomponent of an electronic device; (b) printing a surface of a secondsubstrate with a second printable ink to produce a second component ofan electronic device; and (c) joining said printed surfaces of saidfirst and second substrates in facing relation such that said first andsecond components produce a functional electronic device.
 2. The methodof claim 1 wherein said first and second substrates are fabricated fromflexible material.
 3. The method of claim 1 wherein said electronicdevice is a thermochromic battery tester device.
 4. The method of claim1 further comprising performing printing step (a) and printing step (b)in a press.
 5. The method of claim 4 wherein said press is a rotogravurepress.
 6. The method of claim 1 wherein step (c) comprises passing saidfirst and second substrates simultaneously through a laminationapparatus, substantially continuously monitoring at least onecharacteristic of at least one of said first and second substrates,bringing one of said first and second substrates into registration withthe other of said first and second substrates in response to saidmonitoring, and uniting said first and second substrates intoregistration.
 7. Apparatus for manufacturing an electronic device, saidapparatus comprising:means for printing a surface of a first substratewith a first printable ink to produce a first conductive component of anelectronic device; means for printing a surface of a second substratewith a second printable ink to produce a second component of anelectronic device; and means for joining said printed surfaces of saidfirst and second substrates in facing relation such that said first andsecond components produce a functional electronic device.
 8. Theapparatus of claim 7 wherein said means for printing comprise means forprinting on substrates fabricated from flexible material.
 9. Theapparatus of claim 7 wherein said electronic device is a thermochromicbattery tester device.
 10. The apparatus of claim 7 wherein said meansfor printing a first substrate and means for printing a second substratecomprise printing stations of a press.
 11. The apparatus of claim 10wherein said press is a rotogravure press.
 12. The apparatus of claim 7wherein said means for joining said printed surfaces comprise means forlaminating said first and second substrates.
 13. The apparatus of claim12 wherein said laminating means comprise means for substantiallycontinuously monitoring at least one characteristic of at least one ofsaid first and second substrates as said substrates pass through saidlaminating means, means for bringing one of said first and secondsubstrates into registration with the other of said first and secondsubstrates in response to said monitoring, and means for uniting saidfirst and second substrates into registration.